<!DOCTYPE html>
<html>
<head>
<title>Multi-Arrow Links</title>
<meta name="description" content="A custom Link geometry that draws arrowheads at the end of each segment of orthogonally routed links." />
<!-- Copyright 1998-2016 by Northwoods Software Corporation. -->
<meta charset="UTF-8">
<script src="go.js"></script>
<link href="../assets/css/goSamples.css" rel="stylesheet" type="text/css"/>  <!-- you don't need to use this -->
<script src="goSamples.js"></script>  <!-- this is only for the GoJS Samples framework -->
<script id="code">
  function init() {
    if (window.goSamples) goSamples();  // init for these samples -- you don't need to call this
    var $ = go.GraphObject.make;

    myDiagram =
      $(go.Diagram, "myDiagramDiv", // the ID of the DIV HTML element
        {
          initialContentAlignment: go.Spot.Center,
          layout: $(go.ForceDirectedLayout),
          "undoManager.isEnabled": true
        });

    myDiagram.nodeTemplate =
      $(go.Node, go.Panel.Auto,
        { locationSpot: go.Spot.Center },
        $(go.Shape,
          {
            figure: "RoundedRectangle",
            parameter1: 10,
            fill: "orange",  // default fill color
            portId: "",
            fromLinkable: true,
            fromSpot: go.Spot.AllSides,
            toLinkable: true,
            toSpot: go.Spot.AllSides,
            cursor: "pointer"
          },
          new go.Binding("fill", "color")),
        $(go.TextBlock,
          { margin: 10, font: "bold 12pt sans-serif" },
          new go.Binding("text"))
      );

    myDiagram.linkTemplate =
      $(MultiArrowLink,  // subclass of Link, defined below
        {
          relinkableFrom: true,
          relinkableTo: true,
          reshapable: true,
          resegmentable: true
        },
        $(go.Shape,
          { isPanelMain: true },
          new go.Binding("fill", "color"))
        // no arrowhead is defined here -- they are hard-coded in MultiArrowLink.makeGeometry
      );

    // create a few nodes and links
    myDiagram.model = new go.GraphLinksModel([
        { key: 1, text: "one", color: "lightyellow" },
        { key: 2, text: "two", color: "brown" },
        { key: 3, text: "three", color: "green" },
        { key: 4, text: "four", color: "slateblue" },
        { key: 5, text: "five", color: "aquamarine" },
        { key: 6, text: "six", color: "lightgreen" },
        { key: 7, text: "seven" }
      ], [
        { from: 5, to: 6, color: "orange" },
        { from: 1, to: 2, color: "red" },
        { from: 1, to: 3, color: "blue" },
        { from: 1, to: 4, color: "goldenrod" },
        { from: 2, to: 5, color: "fuchsia" },
        { from: 3, to: 5, color: "green" },
        { from: 4, to: 5, color: "black" },
        { from: 6, to: 7 }
      ]);
  }


  // Produce a Geometry that includes an arrowhead at the end of each segment.
  // This only works with orthogonal non-Bezier routing.
  function MultiArrowLink() {
    go.Link.call(this);
    this.routing = go.Link.Orthogonal;
  }
  go.Diagram.inherit(MultiArrowLink, go.Link);
  
  // produce a Geometry from the Link's route
  MultiArrowLink.prototype.makeGeometry = function () {
    // get the Geometry created by the standard behavior
    var geo = go.Link.prototype.makeGeometry.call(this);
    if (geo.type !== go.Geometry.Path || geo.figures.length === 0) return geo;
    var mainfig = geo.figures.elt(0);  // assume there's just one PathFigure
    var mainsegs = mainfig.segments;

    var arrowLen = 8;  // length for each arrowhead
    var arrowWid = 3;  // actually half-width of each arrowhead
    var fx = mainfig.startX;
    var fy = mainfig.startY;
    for (var i = 0; i < mainsegs.length; i++) {
      var a = mainsegs.elt(i);
      // assume each arrowhead is a simple triangle
      var ax = a.endX;
      var ay = a.endY;
      var bx = ax;
      var by = ay;
      var cx = ax;
      var cy = ay;
      if (fx < ax - arrowLen) {
        bx -= arrowLen; by += arrowWid;
        cx -= arrowLen; cy -= arrowWid;
      } else if (fx > ax + arrowLen) {
        bx += arrowLen; by += arrowWid;
        cx += arrowLen; cy -= arrowWid;
      } else if (fy < ay - arrowLen) {
        bx -= arrowWid; by -= arrowLen;
        cx += arrowWid; cy -= arrowLen;
      } else if (fy > ay + arrowLen) {
        bx -= arrowWid; by += arrowLen;
        cx += arrowWid; cy += arrowLen;
      }
      geo.add(new go.PathFigure(ax, ay, true)
              .add(new go.PathSegment(go.PathSegment.Line, bx, by))
              .add(new go.PathSegment(go.PathSegment.Line, cx, cy).close()));
      fx = ax;
      fy = ay;
    }

    return geo;
  };
</script>
</head>
<body onload="init()">
<div id="sample">
  <div id="myDiagramDiv" style="border: solid 1px blue; width:100%; height:700px; min-width: 200px"></div>
  <p>
  This sample demonstrates customization of the <a>Link</a> <a>Shape</a>'s <a>Geometry</a>.
  </p>
  <p>
  The MultiArrowLink class in this sample inherits from Link and overrides the <a>Link.makeGeometry</a> method
  to add arrowheads at the end of each interior segment, assuming that the route is orthogonal.
  </p>
</div>
</body>
</html>
